Biometric task network

ABSTRACT

Output can be provided from a selected biometric analysis task that is one of a plurality of biometric analysis tasks based on an image provided from an image sensor. The selected biometric analysis task can be performed in a deep neural network that includes a common feature extraction neural network, a plurality of biometric task-specific neural networks and a plurality of expert pooling neural networks that perform the plurality of biometric analysis tasks by inputting the image to the common feature extraction network to determine latent variables. The latent variables can be input to the plurality of biometric task-specific neural networks to determine a plurality of first outputs. Concatenated first output results can be formed and the concatenated plurality of first result outputs and the latent variables can be input to the plurality of expert pooling neural networks to determine one or more biometric analysis task outputs.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority to U.S. Provisional Patent Application No. 63/310,401 filed on Feb. 15, 2022, which is hereby incorporated by reference in its entirety.

BACKGROUND

Images can be acquired by sensors and processed using a computer to determine data regarding objects in an environment around a system. Operation of a sensing system can include acquiring accurate and timely data regarding objects in the system's environment. A computer can acquire images from one or more image sensors that can be processed to determine data regarding objects. Data extracted from images of objects can be used by a computer to operate systems including vehicles, robots, security, and object tracking systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example traffic infrastructure system.

FIG. 2 is a diagram of an example biometric image.

FIG. 3 is a diagram of an example biometric system.

FIG. 4 is a diagram of an example multi-task biometric system.

FIG. 5 is a diagram of example multi-task biometric system including expert pooling.

FIG. 6 is a flowchart diagram of an example process to train a deep neural network to perform biometric analysis tasks.

FIG. 7 is a flowchart diagram of an example process to train a deep neural network including expert pooling to perform biometric analysis tasks.

FIG. 8 is a flowchart diagram of an example process to authenticate a user with a deep neural network.

DETAILED DESCRIPTION

Biometric analysis can be implemented in a computer to determine data regarding objects, for example potential users, in or around system or machine, such as a vehicle. Based on data determined from biometric analysis a vehicle, for example, can be operated. Biometric analysis herein means measuring, or making a determination based on measuring, data regarding a user based on physical characteristics of the user. For example, a computing device in a vehicle or traffic infrastructure system can be programmed to acquire one or more images from one or more sensors included in the vehicle or the traffic infrastructure system and grant permission for a user to operate the vehicle based on biometric data determined based on the images. This granting of permission can rely on biometric identification. Biometric identification means determining the identity of a potential user based on analyzing biometric data. The determined identity of a user can be logged to keep track of which user is accessing a vehicle or compared to a list of authorized users to authenticate a user prior to granting permission to the user to operate a vehicle or system. In addition to biometric identification, biometric analysis can include determining one or more physical characteristics such as user drowsiness, gaze direction, user pose, user liveliness, etc. Biometric analysis tasks can be implemented in various machines or systems, in addition to vehicles. For example, a computer system, a robot system, a manufacturing system, and a security system can require that a potential user be identified using an acquired image before granting access to the system or a secure area.

Advantageously, techniques described herein can enhance the ability of a computing device in a traffic infrastructure system to perform biometric analysis based on a recognition that facial biometric algorithms such as facial feature identification include redundant tasks across different applications. Further, some facial biometric algorithms have sparse or limited training datasets. Techniques described herein include a multi-task network that includes a common feature identification neural network and a plurality of biometric analysis task neural networks. A deep neural network is configured to include a common feature extraction neural network as a “backbone” and a plurality of biometric analysis task neural networks that receive as input a common set of latent variables generated by the common feature extraction neural network. The deep neural network includes a plurality of expert pooling deep neural networks that enhance training of the deep neural network by sharing results between the plurality of biometric analysis tasks.

Disclosed herein is a method, including providing output from a selected biometric analysis task that is one of a plurality of biometric analysis tasks based on an image provided from an image sensor, wherein the selected biometric analysis task is performed in a deep neural network that includes a common feature extraction neural network, a plurality of biometric task-specific neural networks and a plurality of expert pooling neural networks that perform the plurality of biometric analysis tasks by inputting the image to the common feature extraction network to determine latent variables. The latent variables can be input to the plurality of biometric task-specific neural networks to determine a plurality of first outputs. The plurality of first outputs can be concatenated to form concatenated first outputs. The concatenated first outputs and the latent variables can be input to the plurality of expert pooling neural networks to determine one or more biometric analysis task outputs and one or more biometric analysis task outputs can be selected and output.

A device can be operated based on the selected biometric analysis task output. The plurality of biometric analysis tasks can include biometric identification, liveliness determination, drowsiness determination, gaze determination, pose determination, and facial feature segmentation. The common feature extraction neural network can include a plurality of convolutional layers. The plurality of biometric task-specific neural networks can include a plurality of fully connected layers. The plurality of expert pooling neural networks can include a plurality of fully connected layers. The one or more of first outputs from the plurality of biometric task-specific neural networks can be input to a SoftMax function before being concatenated. One or more of the outputs from the plurality of expert pooling neural networks can be input to a SoftMax function before being output as biometric analysis task outputs. One or more of the biometric analysis task outputs can be set to zero during training. The deep neural network can be trained by combining the biometric analysis task outputs with ground truth to determine a joint loss function. The joint loss function can be backpropagated through the deep neural network to determine weights. The deep neural network can be configured to include the common feature extraction network and a subset of the biometric task-specific neural networks during inference based on a selected biometric analysis task. The deep neural network can be trained based on a loss function determined based on sparse-categorical-cross-entropy statistics. The deep neural network can be trained based on a loss function determined based on mean-square-error statistics.

Further disclosed is a computer readable medium, storing program instructions for executing some or all of the above method steps. Further disclosed is a computer programmed for executing some or all of the above method steps, including a computer apparatus, programmed to provide output from a selected biometric analysis task that is one of a plurality of biometric analysis tasks based on an image provided from an image sensor, wherein the selected biometric analysis task is performed in a deep neural network that includes a common feature extraction neural network, a plurality of biometric task-specific neural networks and a plurality of expert pooling neural networks that perform the plurality of biometric analysis tasks by inputting the image to the common feature extraction network to determine latent variables. The latent variables can be input to the plurality of biometric task-specific neural networks to determine a plurality of first outputs. The plurality of first outputs can be concatenated to form concatenated first outputs. The concatenated first outputs and the latent variables can be input to the plurality of expert pooling neural networks to determine one or more biometric analysis task outputs and one or more biometric analysis task outputs can be selected and output.

The instructions can include further instructions to operate a device based on the selected biometric analysis task output. The plurality of biometric analysis tasks can include biometric identification, liveliness determination, drowsiness determination, gaze determination, pose determination, and facial feature segmentation. The common feature extraction neural network can include a plurality of convolutional layers. The plurality of biometric task-specific neural networks can include a plurality of fully connected layers. The plurality of expert pooling neural networks can include a plurality of fully connected layers. The one or more of first outputs from the plurality of biometric task-specific neural networks can be input to a SoftMax function before being concatenated. One or more of the outputs from the plurality of expert pooling neural networks can be input to a SoftMax function before being output as biometric analysis task outputs. One or more of the biometric analysis task outputs can be set to zero during training. The deep neural network can be trained by combining the biometric analysis task outputs with ground truth to determine a joint loss function. The joint loss function can be backpropagated through the deep neural network to determine weights. The deep neural network can be configured to include the common feature extraction network and a subset of the biometric task-specific neural networks during inference based on a selected biometric analysis task. The deep neural network can be trained based on a loss function determined based on sparse-categorical-cross-entropy statistics. The deep neural network can be trained based on a loss function determined based on mean-square-error statistics.

FIG. 1 is a diagram of a sensing system 100 that can include a traffic infrastructure node 105 that includes a server computer 120 and stationary sensors 122. Sensing system 100 includes a vehicle 110, operable in autonomous (“autonomous” by itself in this disclosure means “fully autonomous”), semi-autonomous, and occupant piloted (also referred to as non-autonomous) mode. One or more vehicle 110 computing devices 115 can receive data regarding the operation of the vehicle 110 from sensors 116. The computing device 115 may operate the vehicle 110 in an autonomous mode, a semi-autonomous mode, or a non-autonomous mode.

The computing device 115 includes a processor and a memory such as are known. Further, the memory includes one or more forms of computer-readable media, and stores instructions executable by the processor for performing various operations, including as disclosed herein. For example, the computing device 115 may include programming to operate one or more of vehicle brakes, propulsion (e.g., control of acceleration in the vehicle 110 by controlling one or more of an internal combustion engine, electric motor, hybrid engine, etc.), steering, climate control, interior and/or exterior lights, etc., as well as to determine whether and when the computing device 115, as opposed to a human operator, is to control such operations.

The computing device 115 may include or be communicatively coupled to, e.g., via a vehicle communications bus as described further below, more than one computing devices, e.g., controllers or the like included in the vehicle 110 for monitoring and/or controlling various vehicle components, e.g., a powertrain controller 112, a brake controller 113, a steering controller 114, etc. The computing device 115 is generally arranged for communications on a vehicle communication network, e.g., including a bus in the vehicle 110 such as a controller area network (CAN) or the like; the vehicle 110 network can additionally or alternatively include wired or wireless communication mechanisms such as are known, e.g., Ethernet or other communication protocols.

Via the vehicle network, the computing device 115 may transmit messages to various devices in the vehicle and/or receive messages from the various devices, e.g., controllers, actuators, sensors, etc., including sensors 116. Alternatively, or additionally, in cases where the computing device 115 actually comprises multiple devices, the vehicle communication network may be used for communications between devices represented as the computing device 115 in this disclosure. Further, as mentioned below, various controllers or sensing elements such as sensors 116 may provide data to the computing device 115 via the vehicle communication network.

In addition, the computing device 115 may be configured for communicating through a vehicle-to-infrastructure (V-to-I) interface 111 with a remote server computer 120, e.g., a cloud server, via a network 130, which, as described below, includes hardware, firmware, and software that permits computing device 115 to communicate with a remote server computer 120 via a network 130 such as wireless Internet (WI-FI®) or cellular networks. V-to-I interface 111 may accordingly include processors, memory, transceivers, etc., configured to utilize various wired and/or wireless networking technologies, e.g., cellular, BLUETOOTH® and wired and/or wireless packet networks. Computing device 115 may be configured for communicating with other vehicles 110 through V-to-I interface 111 using vehicle-to-vehicle (V-to-V) networks, e.g., according to Dedicated Short Range Communications (DSRC) and/or the like, e.g., formed on an ad hoc basis among nearby vehicles 110 or formed through infrastructure-based networks. The computing device 115 also includes nonvolatile memory such as is known. Computing device 115 can log data by storing the data in nonvolatile memory for later retrieval and transmittal via the vehicle communication network and a vehicle to infrastructure (V-to-I) interface 111 to a server computer 120 or user mobile device 160.

As already mentioned, generally included in instructions stored in the memory and executable by the processor of the computing device 115 is programming for operating one or more vehicle 110 components, e.g., braking, steering, propulsion, etc., without intervention of a human operator. Using data received in the computing device 115, e.g., the sensor data from the sensors 116, the server computer 120, etc., the computing device 115 may make various determinations and/or control various vehicle 110 components and/or operations without a driver to operate the vehicle 110. For example, the computing device 115 may include programming to regulate vehicle 110 operational behaviors (i.e., physical manifestations of vehicle 110 operation) such as speed, acceleration, deceleration, steering, etc., as well as tactical behaviors (i.e., control of operational behaviors typically in a manner intended to achieve efficient traversal of a route) such as a distance between vehicles and/or amount of time between vehicles, lane-change, minimum gap between vehicles, left-turn-across-path minimum, time-to-arrival at a particular location and intersection (without signal) minimum time-to-arrival to cross the intersection.

Controllers, as that term is used herein, include computing devices that typically are programmed to monitor and/or control a specific vehicle subsystem. Examples include a powertrain controller 112, a brake controller 113, and a steering controller 114. A controller may be an electronic control unit (ECU) such as is known, possibly including additional programming as described herein. The controllers may communicatively be connected to and receive instructions from the computing device 115 to actuate the subsystem according to the instructions. For example, the brake controller 113 may receive instructions from the computing device 115 to operate the brakes of the vehicle 110.

The one or more controllers 112, 113, 114 for the vehicle 110 may include known electronic control units (ECUs) or the like including, as non-limiting examples, one or more powertrain controllers 112, one or more brake controllers 113, and one or more steering controllers 114. Each of the controllers 112, 113, 114 may include respective processors and memories and one or more actuators. The controllers 112, 113, 114 may be programmed and connected to a vehicle 110 communications bus, such as a controller area network (CAN) bus or local interconnect network (LIN) bus, to receive instructions from the computing device 115 and control actuators based on the instructions.

Sensors 116 may include a variety of devices known to provide data via the vehicle communications bus. For example, a radar fixed to a front bumper (not shown) of the vehicle 110 may provide a distance from the vehicle 110 to a next vehicle in front of the vehicle 110, or a global positioning system (GPS) sensor disposed in the vehicle 110 may provide geographical coordinates of the vehicle 110. The distance(s) provided by the radar and/or other sensors 116 and/or the geographical coordinates provided by the GPS sensor may be used by the computing device 115 to operate the vehicle 110 autonomously or semi-autonomously, for example.

The vehicle 110 is generally a land-based vehicle 110 capable of autonomous and/or semi-autonomous operation and having three or more wheels, e.g., a passenger car, light truck, etc. The vehicle 110 includes one or more sensors 116, the V-to-I interface 111, the computing device 115 and one or more controllers 112, 113, 114. The sensors 116 may collect data related to the vehicle 110 and the environment in which the vehicle 110 is operating. By way of example, and not limitation, sensors 116 may include, e.g., altimeters, cameras, LIDAR, radar, ultrasonic sensors, infrared sensors, pressure sensors, accelerometers, gyroscopes, temperature sensors, pressure sensors, hall sensors, optical sensors, voltage sensors, current sensors, mechanical sensors such as switches, etc. The sensors 116 may be used to sense the environment in which the vehicle 110 is operating, e.g., sensors 116 can detect phenomena such as weather conditions (precipitation, external ambient temperature, etc.), the grade of a road, the location of a road (e.g., using road edges, lane markings, etc.), or locations of target objects such as neighboring vehicles 110. The sensors 116 may further be used to collect data including dynamic vehicle 110 data related to operations of the vehicle 110 such as velocity, yaw rate, steering angle, engine speed, brake pressure, oil pressure, the power level applied to controllers 112, 113, 114 in the vehicle 110, connectivity between components, and accurate and timely performance of components of the vehicle 110.

Vehicles can be equipped to operate in both autonomous and occupant piloted mode. By a semi- or fully-autonomous mode, we mean a mode of operation wherein a vehicle can be piloted partly or entirely by a computing device as part of a system having sensors and controllers. The vehicle can be occupied or unoccupied, but in either case the vehicle can be partly or completely piloted without assistance of an occupant. For purposes of this disclosure, an autonomous mode is defined as one in which each of vehicle propulsion (e.g., via a powertrain including an internal combustion engine and/or electric motor), braking, and steering are controlled by one or more vehicle computers; in a semi-autonomous mode the vehicle computer(s) control(s) one or more of vehicle propulsion, braking, and steering. In a non-autonomous mode, none of these are controlled by a computer.

A traffic infrastructure node 105 can include a physical structure such as a tower or other support structure (e.g., a pole, a box mountable to a bridge support, cell phone tower, road sign support, etc.) on which infrastructure sensors 122, as well as server computer 120 can be mounted, stored, and/or contained, and powered, etc. One traffic infrastructure node 105 is shown in FIG. 1 for ease of illustration, but the system 100 could and likely would include tens, hundreds, or thousands of traffic infrastructure nodes 105. The traffic infrastructure node 105 is typically stationary, i.e., fixed to and not able to move from a specific geographic location. The infrastructure sensors 122 may include one or more sensors such as described above for the vehicle 110 sensors 116, e.g., lidar, radar, cameras, ultrasonic sensors, etc. The infrastructure sensors 122 are fixed or stationary. That is, each sensor 122 is mounted to the infrastructure node so as to have a substantially unmoving and unchanging field of view.

Server computer 120 typically has features in common with the vehicle 110 V-to-I interface 111 and computing device 115, and therefore will not be described further to avoid redundancy. Although not shown for ease of illustration, the traffic infrastructure node 105 also includes a power source such as a battery, solar power cells, and/or a connection to a power grid. A traffic infrastructure node 105 server computer 120 and/or vehicle 110 computer 115 can receive sensor 116, 122 data to monitor one or more objects. An “object,” in the context of this disclosure, is a physical, i.e., material, structure detected by a vehicle sensor 116 and/or infrastructure sensor 122. An object may be a biological object such as a human. A server computer 120 and/or computing device 115 can perform biometric analysis on object data acquired by a sensor 116/122.

FIG. 2 is a diagram of an image acquisition system 200 included in a vehicle 110 or traffic infrastructure node 105. Image 202 can be acquired by a camera 206, which can be a sensor 116, 122, having a field of view 208. The image 202 can be acquired when a user approaches a vehicle 110, for example. A computing device 115 in the vehicle 110 or a server computer 120 can execute a biometric analysis task that authenticates the user and grants permission to the user to operate the vehicle 110, i.e., unlocks a door to permit the user to enter the vehicle 110. In addition to biometric identification, spoof detection biometric analysis tasks such as liveliness detection can be used to determine whether the image data presented for user identification is a real image of a real user, i.e., not a photograph of a user or not a mask of a user.

Other biometric analysis tasks based on images of a user such as are known include drowsiness detection, head pose detection, gaze detection, and emotion detection. Drowsiness detection can determine a user's state of alertness typically by analyzing eyelid position and blink rates. Head pose detection can also determine a user's state of alertness and attention to vehicle operation, typically by analyzing location and orientation of a user's face to detect nodding and slumping postures. Gaze detection can determine the direction in which a user's eyes are looking to determine whether the user is paying attention to vehicle operation. Emotion detection can determine an emotional state of a user, i.e., is a user agitated or frightened, to detect possible distractions from vehicle operation.

FIG. 3 is a diagram of a biometric analysis task system 300. A biometric analysis task system 300 can be implemented in a server computer 120 or computing device 115, for example. Biometric analysis tasks including user identification, spoof detection, drowsiness detection, head pose detection, and gaze detection share common computational tasks 304, such as determining a location and orientation of a user's face in an image 302. Other common computational tasks include determining location and size of facial features such as eyes, mouth, and nose. FIG. 3 illustrates an image 302 being input to common computational tasks 304 to determine common facial feature data such as location, orientation, and features, for example. The common facial feature data can be input to biometric analysis tasks 306, 308, 310 to determine biometric tasks outputs 312, 314, 316. The biometric task outputs can be 312, 314, 316 one or more of user identification, spoof detection, drowsiness detection, head pose detection, gaze detection, and emotion detection etc.

FIG. 4 is a diagram of a biometric analysis task system implemented as a deep neural network (DNN) 400 configured to input an image 402 into a plurality of convolutional layers 404, 406, 408 that are included in a common feature extraction convolutional neural network (CNN) 410. A biometric analysis task system implemented as a DNN 400 can be executed on a server computer 120 or computing device 115. The common feature extraction or “backbone” CNN 410 extracts common facial features from image data and outputs latent variables. Latent variables in the DNN 400 represent common facial features output by CNN 410 in response to an input image 402 that includes a human face. CNN 410 is trained as described herein to process an image 402 to determine the location of a human face and determine facial features indicating the location, orientation, and size of human facial features such as eyes, nose, and mouth. CNN 410 can also determine facial features such as skin tone, texture and presence/absence of facial hair, and presence/absence of objects such as glasses and body piercings. The facial features are referred to as common facial features because they are output as latent variables in common to a plurality of biometric analysis task neural networks 412, 414, 416, 418, 420 and a segmentation neural network 422. Biometric analysis task neural networks 412, 414, 416, 418, 420 include a plurality of fully connected layers that can perform tasks such as biometric identification, spoof detection including liveliness, drowsiness detection, head pose detection, gaze detection, and emotion detection. Segmentation neural network 422 can perform facial feature segmentation by determining regions in an image of a user's face that can include features such as eyes, teeth, lips, nose, and facial skin, for example.

Biometric analysis task neural networks 412, 414, 416, 418, 420 and segmentation neural network 422 are trained to output predictions regarding the biometric analysis tasks or segmentation task based on latent variables output from the common feature extraction CNN 410. Predictions output from the biometric analysis tasks include biometric identification of a user. A biometric identification prediction is a probability that an input image includes a human face that matches a human face that the DNN 400 was previously trained to recognize. A liveliness prediction is a probability that the image 402 includes a live user, as opposed to a photograph or mask of a user. A drowsiness prediction is a probability that the image 402 includes a user experiencing drowsiness. A head pose prediction are estimates of the roll, pitch, and yaw of a user's head. An emotion prediction is a probability that the user is experiencing a strong emotion such as anger or fear. A facial segmentation prediction is an image with regions which indicate the locations of facial features.

DNN 400 can include SoftMax functions 424, 426, 428, 430, 432 on the output of the biometric analysis task neural networks 412, 414, 416, 418, 420, respectively. The SoftMax functions 424, 426, 428, 430, 432 are functions that turn a vector of K real values into a vector of K real values between 0 and 1 that sum to 1. Output from the SoftMax functions 424, 426, 428, 430, 432 can be output as results of the biometric analysis tasks or used to calculate loss functions. Processing the outputs of the biometric analysis task neural networks 412, 414, 416, 418, 420 with SoftMax functions 424, 426, 428, 430, 432 permits the outputs to be combined into a joint loss function for training the DNN 400. A loss function compares the output from a SoftMax function 424, 426, 428, 430, 432 connected to a biometric analysis task neural network 412, 414, 416, 418, 420 with a ground truth value to determine how closely the biometric analysis task neural network has come to determining a correct result. A SoftMax function 424, 426, 428, 430, 432, by limiting the output from each biometric analysis task neural network 412, 414, 416, 418, 420 to values between 0 and 1 prevents one or more of the outputs from dominating the calculation of a joint loss function due to numerical differences in the outputs. A joint loss function is determined by combining the individual loss functions for each biometric analysis task neural network 412, 414, 416, 418, 420, typically by adding the individual loss functions together.

Training a DNN 400 can include determining a training dataset of images 402 and ground truth for each image 402. Determining ground truth can include inspecting the images 402 in the training dataset and estimating the correct result to be expected from a SoftMax function 424, 426, 428, 430, 432 connected to a biometric analysis task neural network 412, 414, 416, 418, 420. During training an image 402 can be input to the DNN 400 a plurality of times. Each time the image 402 is input, weights or parameters that control the operation of the convolutional layers 404, 406, 408, of the CNN 410 and the fully connected layers of the biometric analysis task neural networks 412, 414, 416, 418, 420 can be altered and a joint loss function based on the outputs and the ground truth values for each output can be determined. The joint loss function can be backpropagated through the DNN 400 to select the weights for each layer that result in the lowest joint loss, i.e., the most correct results. Backpropagation is a process for applying the joint loss function to the weights of the DNN 400 layers starting at the layers closest to the output and progressing back to the layers closest to the input. By processing a plurality of input images 402 including ground truth in the training dataset a plurality of times, a set of weights for the layers of the DNN 400 can be selected that converge on correct results for the entire training dataset the DNN 400 can be determined. Selecting an optimum set of weights in this fashion is referred to as training the DNN 400.

Segmentation determines regions in an image indicating the different facial features. Segmentation labels the regions according to segment classes, where each segment class indicates a different facial feature. Example segment classes include left eye, right eye, teeth, upper lip, lower lip, nose, facial skin, left eyebrow, right eyebrow, etc. The number of facial segmentation classes can be equal to 14 or more for a typical segmentation neural network 422. Each segment is further specified by its location, shape, and number of pixels included in the segment. In determining a loss function, the segments in a predicted segmented image output by segmentation neural network 422 can be compared to the segments in a ground truth segmented image. Comparing segments includes determining that the pixels of a predicted segment overlap with the pixels of a ground truth segment having the same class designation. The comparison can be qualitative, based on sparse-categorical-cross-entropy statistics, which requires that a percentage, for example 50%, of the ground truth segment pixels are overlapped with a predicted segment with the same class designation. In other examples the comparison can be quantitative, based on mean-square-error statistics which count the number of non-overlapped pixels in the ground truth segments and take the square of the number of non-overlapped pixels.

Training the DNN 400 using a joint loss function can advantageously compensate for differences in training datasets for each biometric analysis task. The quality of training for a biometric task can be dependent upon the number of images available with appropriate ground truth for each biometric analysis task. For example, biometric identification tasks can benefit from the existence of large commercially available datasets that include ground truth. Other biometric analysis tasks, such as drowsiness determination or gaze determination can require that a user acquire image data and estimate ground truth manually. Advantageously, training DNN 400 using a joint loss function determined as discussed herein can permit sharing training datasets between biometric analysis tasks having large training datasets with biometric analysis tasks having smaller training datasets. For example, the individual loss functions can be weighted as they are combined to form a joint loss function to give more weight to loss functions that include larger training datasets.

In examples where one or more of the biometric analysis tasks can have small amounts of ground truth data to include in a training dataset, training the DNN 400 can be enhanced by branch training isolation. Branch training isolation sets the output from a biometric analysis task neural network having no ground truth data for a particular image in a training dataset to a null value. Setting the output from a biometric analysis task neural network to a null value also sets the loss function determined for the biometric analysis task neural network to zero. Branch training isolation also freezes the weights included in the biometric analysis task neural network for that image. This permits the biometric analysis task neural network to be available for joint training along with the rest of the DNN 400 without penalizing biometric analysis tasks with sparse training datasets. For example, drowsiness detection typically has fewer images with ground truth than identification tasks.

FIG. 5 is a diagram of a DNN 500, which like the DNN 400 can be implemented on a variety of computing devices, configured to enhance training and inference over the DNN 400 illustrated in FIG. 4 by combining data from biometric analysis task neural networks 506, 508, 510, 512, 514 using expert pooling. DNN 500 inputs an image 502 to a common feature extraction CNN 504. Latent variables output from the common feature extraction CNN 504, i.e., facial features, is output to biometric analysis task neural networks 506, 508, 510, 512, 514 and segmentation neural network 516. Biometric analysis task neural networks 506, 508, 510, 512, 514 are as defined in relation to biometric analysis task neural networks 412, 414, 416, 418, 420 in FIG. 4 , above. Output from biometric analysis task neural networks 506, 508, 510, 512, 514 are output to SoftMax functions 518, 520, 522, 524, 526 prior to being output to concatenation 528. Concatenation 528 combines the outputs from biometric analysis task neural networks 506, 508, 510, 512, 514 and segmentation neural network 516 by concatenating them into a single vector that is output to expert pooling neural networks 530, 532, 534, 536, 538, 540.

Expert pooling neural networks 530, 532, 534, 536, 538, 540 include a plurality of fully connected layers that input the concatenated vector from concatenation 528 and skip-connected latent vectors output from common feature extraction CNN 504 are input to expert pooling neural networks 530, 532, 534, 536, 538, 540 to recalculate biometric analysis tasks including data from concatenation 528. Skip-connecting means connecting output from a layer of a DNN 500 to another layer further along the processing sequence of the DNN 500 while by-passing or “skipping” an intermediate layer. Expert pooling neural networks 530, 532, 534, 536, 538, 540 permit sharing data from biometric analysis tasks with large training datasets with biometric analysis tasks having smaller training datasets as discussed above in relation to FIG. 4 . Output from expert pooling neural networks 530, 532, 534, 536, 538, 540 is output to SoftMax functions 542, 544, 546, 548, 550, respectively and segmentation output 552. Output from SoftMax functions 542, 544, 546, 548, 550 and segmentation output 552 can be output as results of biometric analysis tasks to a computing device 115 to be used in operation of a vehicle 110 or can be input to calculate a joint loss function for training the DNN 500 as discussed above in relation to FIG. 4 .

Following training, a DNN 500 can be transmitted to a computing device 115 in a vehicle 110 to perform biometric analysis tasks on image data acquired by sensors 116 included the vehicle 110. Biometric analysis tasks can benefit from joint knowledge determined encoded in the common feature extraction CNN 504, however, not all biometric analysis tasks are required for all applications of DNN 500. For example, facial feature segmentation tasks can enhance training of biometric identification tasks, however, outputs from facial feature segmentation tasks may not be required at inference time to enhance biometric identification task accuracy. Inference time refers to operation of a DNN 400 in use following completion of training. At inference time, a sub-graph which includes a subset of the biometric analysis task neural networks can be determined which can provide selected biometric analysis task output. Selecting a subset of the biometric analysis task neural networks can reduce the amount of memory required to store and execute DNN 400 and reduce the time and computer resources required to execute DNN 400.

Sub-graph generation can be determined based on the biometric analysis tasks required for a particular application. Table 1 includes examples of sub-graph generation. Note that all tasks require common feature extraction (“backbone”) layers of the DNN 500.

-   -   1. Convenience identification: backbone, biometric         identification, liveliness determination     -   2. Strong identification: backbone, biometric identification,         facial feature segmentation, liveliness determination     -   3. User stress: backbone, biometric identification, emotion         determination     -   4. User engagement: backbone, pose determination, gaze         determination

Table 1. Sub-Graph Generation

In addition to sub-graph generation, some biometric analysis tasks can be performed conditionally. For example, if the common feature extraction CNN 504 determines that the feature extraction confidence is low, the input to the liveliness biometric analysis task could be masked to be 0. Because computing devices 115 that include hardware accelerators typically skip multiplications with 0's, masking inputs to biometric analysis tasks with 0's can further reduce run time when feature extraction confidence is low.

FIG. 6 is a flowchart, described in relation to FIGS. 1-4 of a process 600 for training a DNN 400 including a common feature extraction CNN 410, a plurality of biometric analysis task neural networks 412, 414, 416, 418, 420 and a segmentation neural network 422. Process 600 can be implemented by a processor of a computing device 115 or server computer 120, taking as input image data from sensors 116, 122, executing commands, and outputting biometric analysis task predictions. A DNN 400 is typically executed on a server computer 120 on a traffic infrastructure node 105 at training time and transmitted to a computing device 115 in a vehicle 110 for operation at inference time. Process 600 includes multiple blocks that can be executed in the illustrated order. Process 600 could alternatively or additionally include fewer blocks or can include the blocks executed in different orders.

Process 600 begins at block 602, where an image 402 is acquired from a training dataset. Image 402 includes ground truth for one or more biometric analysis tasks as discussed above in relation to FIG. 3 . In examples where ground truth is not available for one or more biometric analysis tasks, the output from the one or more biometric analysis task neural networks 412, 414, 416, 418, 420 or the segmentation task neural network 422 can be set to a null value and the weights for the one or more biometric analysis task neural networks 412, 414, 416, 418, 420 or the segmentation task neural network 422 can be frozen. Freezing a neural network prevents the weights that program the neural network from being updated based on backpropagating a joint loss function determined at block 610.

At block 604 the image 402 is input to a common feature extraction CNN 410 to determine facial features to be output as latent variables as discussed in relation to FIG. 4 , above.

At block 606 the latent variables are input to a plurality of biometric analysis task neural networks 412, 414, 416, 418, 420 or the segmentation task neural network 422 which process the latent variables to determine predictions regarding the input image 402 as discussed above in relation to FIG. 4 . At inference time the predictions can be output to a computing device 115 to be used to operate a vehicle 110.

At block 608, at training time, the predictions output from biometric analysis task neural networks 412, 414, 416, 418, 420 are input to SoftMax functions 424, 426, 428, 430, 432 to condition the output predictions to be between 0 and 1. Conditioning the output predictions permits the output predictions to be combined at block 610 into a joint loss function without one or more of the output predictions numerically dominating the calculations.

At block 610 the output from the SoftMax functions 424, 416, 428, 430, 432 and the segmentation neural network 422 are combined with ground truth to determine a joint loss function for the DNN 400 in response to an input image 402.

At block 612 the joint loss function can be backpropagated through the layers of the DNN 400 to determine optimal weights for the layers of the DNN 400. Optimal weights are the weights that result in outputs that most closely match the ground truth included in the training dataset. As discussed above in relation to FIG. 4 , training DNN 400 includes inputting an input image 402 a plurality of times while varying the weights that program the layers of the DNN 400. Training the DNN 400 includes selecting weights for the layers of DNN 400 that provide the lowest joint loss function for the greatest number of input images 402 in the training dataset. Following block 612 process 600 ends.

FIG. 7 is a flowchart, described in relation to FIGS. 1-5 , of a process 700 for training a DNN 500 including a common feature extraction CNN 504, a plurality of biometric analysis task neural networks 506, 508, 510, 512, 514 and a segmentation neural network 516. Process 700 can be implemented by a processor of a computing device 115 or server computer 120, taking as input image data from sensors 116, 122, executing commands, and outputting biometric analysis task predictions. A DNN 500 is typically executed on a server computer 120 on a traffic infrastructure node 105 at training time and transmitted to a computing device 115 in a vehicle 110 for operation at inference time. Process 700 could alternatively or additionally include fewer blocks or can include the blocks executed in different orders.

Process 700 begins at block 702, where an image 502 is acquired from a training dataset. Image 502 includes ground truth for one or more biometric analysis tasks as discussed above in relation to FIGS. 4 and 5 . In examples where ground truth is not available for one or more biometric analysis tasks, the output from the one or more biometric analysis tasks can be set to a null value and the weights for the one or more biometric analysis tasks can be frozen to prevent them from being updated based on a joint loss function determined based on the outputs from the biometric analysis tasks.

At block 704 the image 502 is input to a common feature extraction CNN 504 to determine facial features to be output as latent variables as discussed in relation to FIGS. 4 and 5 , above.

At block 706 the latent variables are input to a plurality of biometric analysis task neural networks 506, 508, 510, 512, 514 and a segmentation neural network 516 which process the latent variables to determine first predictions regarding the biometric analysis tasks and facial feature segmentation tasks.

At block 708 the first predictions output from biometric analysis task neural networks 506, 508, 510, 512, 514 are input to SoftMax functions 518, 520, 522, 524, 526 to condition the output predictions to be between 0 and 1.

At block 710 the output from the SoftMax functions 518, 520, 522, 524, 526 and the segmentation neural network 516 is input to concatenation 528 to combine the output from the SoftMax functions 518, 520, 522, 524, 526 and the segmentation neural network 516 into a concatenated vector.

At block 712 the concatenated vector and latent variables from the common feature extraction CNN 504 are input to expert pooling neural networks 530, 532, 534, 536, 538, 540 to recalculate biometric analysis tasks including data from concatenation 528.

At block 714 the predictions output from expert pooling neural networks 530, 532, 534, 536, 538, 540 can be output at inference time to operate a device including a vehicle 110. For example, the output predictions can be used to identify a user and permit access to a device. The output predictions can also be used to determine stress being experiences by a user or determine user alertness, for example. The predictions output from expert pooling neural networks 530, 532, 534, 536, 538, 540 can also be input to SoftMax functions 542, 544, 546, 548, 550 to condition the output to be between 0 and 1.

At block 716 the outputs from Softmax functions 542, 544, 546, 548, 550 can be combined with ground truth to determine a joint loss function for the biometric analysis tasks.

At block 718 the joint loss function can be backpropagated through the layers of the DNN 500 to determine optimal weights for the layers of the DNN 500. Optimal weights are the weights that result in outputs that most closely match the ground truth included in the training dataset. Following block 718 process 700 ends.

FIG. 8 is a flowchart, described in relation to FIGS. 1-7 , of a process 800 for performing a biometric identification task with a DNN 400 including a common feature extraction CNN 410, and two biometric analysis task neural networks 412, 414. Process 800 can be implemented by a processor of a computing device 115 or server computer 120, taking as input image data from sensors 116, 122, executing commands, and outputting biometric analysis task predictions. Process 800 could alternatively or additionally include fewer blocks or can include the blocks executed in different orders.

Following training a DNN 400 as discussed above in relation to FIG. 4 , the trained DNN 400 can be transmitted to a computing device 115 in a device such as a vehicle 110 for inference. As discussed above in relation to FIG. 6 , DNN 400 can be trained with a plurality of biometric analysis task neural networks 412, 414, 416, 418, 420 including a segmentation neural network 422. At inference time, the DNN 400 can be reduced to only include biometric analysis task neural networks that pertain to a specific task. In this example, the DNN 400 will be used for biometric identification and liveliness detection and will include biometric analysis task neural networks 412, 414. Reconfiguring the DNN 400 in this fashion permits training the DNN 400 with a large and varied training dataset that includes training images and ground truth for a plurality of biometric analysis tasks, while providing a lightweight DNN 400 that saves computer resources including memory space and execution time at inference time.

Process 800 begins at block 802 where the vehicle 110 acquires an image 402 using a sensor 116 included in the vehicle 110. Process 800 could also be implemented in a security system, a robot guidance system, or a handheld device such as a cell phone that seeks to determine the identity of a potential user before granting access to a device.

At block 804 the computing device 115 inputs the image 402 to the common feature extraction CNN 410 to determine facial features to output as latent variables.

At block 806 the latent variables are input to biometric analysis task neural networks 412, 414 for biometric identification and liveliness detection to determine predictions regarding a probability that the identity of the user in the input image 402 is the same as the user that the DNN 400 was trained to identify and a probability that the input image 402 includes a live human.

At block 808 the predictions regarding biometric identification and liveliness are output from DNN 400 to the computing device 115 in the vehicle 110.

At block 810 the computing device 115 determines an authentication score for the user in the image 402. The probabilities indicating biometric identification and the probability of liveliness can be multiplied to determine an overall identification score that reflects the probability the user in the image 402 is the correct user and that the image 402 includes a live human.

At block 812 the computing device 115 tests the authentication score from block 810. If the overall identification score is greater than a user-specified threshold, the user is authenticated and process 800 passes to block 814. The threshold can be determined empirically by testing a plurality of spoofed and real input images 402 to determine the distributions of spoofed and real overall identification scores and a threshold that separates the two distributions. If the authentication score is lower than the user-specified threshold the user fails authentication and process 800 ends.

At block 814 the user has passed authentication and the user is granted permission to operate the vehicle 110. This can include unlocking doors to permit entry to the vehicle 110 and turning on the vehicle 110 controls to permit the user to operate the vehicle 110, granting the user permission to operate various vehicle components, such as climate control, infotainment, etc., to name a few examples. Following block 814 process 800 ends.

Computing devices such as those discussed herein generally each includes commands executable by one or more computing devices such as those identified above, and for carrying out blocks or steps of processes described above. For example, process blocks discussed above may be embodied as computer-executable commands.

Computer-executable commands may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java™, C, C++, Python, Julia, SCALA, Visual Basic, Java Script, Perl, HTML, etc. In general, a processor (e.g., a microprocessor) receives commands, e.g., from a memory, a computer-readable medium, etc., and executes these commands, thereby performing one or more processes, including one or more of the processes described herein. Such commands and other data may be stored in files and transmitted using a variety of computer-readable media. A file in a computing device is generally a collection of data stored on a computer readable medium, such as a storage medium, a random access memory, etc.

A computer-readable medium (also referred to as a processor-readable medium) includes any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile media. Instructions may be transmitted by one or more transmission media, including fiber optics, wires, wireless communication, including the internals that comprise a system bus coupled to a processor of a computer. Common forms of computer-readable media include, for example, RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.

All terms used in the claims are intended to be given their plain and ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary in made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.

The term “exemplary” is used herein in the sense of signifying an example, e.g., a reference to an “exemplary widget” should be read as simply referring to an example of a widget.

The adverb “approximately” modifying a value or result means that a shape, structure, measurement, value, determination, calculation, etc. may deviate from an exactly described geometry, distance, measurement, value, determination, calculation, etc., because of imperfections in materials, machining, manufacturing, sensor measurements, computations, processing time, communications time, etc.

In the drawings, the same reference numbers indicate the same elements. Further, some or all of these elements could be changed. With regard to the media, processes, systems, methods, etc. described herein, it should be understood that, although the steps or blocks of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claimed invention. 

1. A system, comprising: a computer that includes a processor and a memory, the memory including instructions executable by the processor to provide output from a selected biometric analysis task that is one of a plurality of biometric analysis tasks based on an image provided from an image sensor; wherein the selected biometric analysis task is performed in a deep neural network that includes a common feature extraction neural network, a plurality of biometric task-specific neural networks and a plurality of expert pooling neural networks that perform the plurality of biometric analysis tasks by: inputting the image to the common feature extraction network to determine latent variables; inputting the latent variables to the plurality of biometric task-specific neural networks to determine a plurality of first outputs; concatenating the plurality of first outputs to form concatenated first outputs; inputting the concatenated first outputs and the latent variables to the plurality of expert pooling neural networks to determine one or more biometric analysis task outputs; and selecting and outputting one or more biometric analysis task outputs.
 2. The system of claim 1, the instructions including further instructions to operate a device based on the selected biometric analysis task output.
 3. The system of claim 1, wherein the plurality of biometric analysis tasks include biometric identification, liveliness determination, drowsiness determination, gaze determination, pose determination, and facial feature segmentation.
 4. The system of claim 1, wherein the common feature extraction neural network includes a plurality of convolutional layers.
 5. The system of claim 1, wherein the plurality of biometric task-specific neural networks include a plurality of fully connected layers.
 6. The system of claim 1, wherein the plurality of expert pooling neural networks include a plurality of fully connected layers.
 7. The system of claim 1, wherein the one or more of first outputs from the plurality of biometric task-specific neural networks are input to a SoftMax function before being concatenated.
 8. The system of claim 1, wherein one or more of the outputs from the plurality of expert pooling neural networks are input to a SoftMax function before being output as biometric analysis task outputs.
 9. The system of claim 1, wherein one or more of the biometric analysis task outputs are set to zero during training.
 10. The system of claim 1, the instructions including further instructions to train the deep neural network by combining the biometric analysis task outputs with ground truth to determine a joint loss function.
 11. The system of claim 10, wherein the joint loss function is backpropagated through the deep neural network to determine weights.
 12. The system of claim 1, wherein the deep neural network is configured to include the common feature extraction network and a subset of the biometric task-specific neural networks during inference based on a selected biometric analysis task.
 13. A method, comprising: providing output from a selected biometric analysis task that is one of a plurality of biometric analysis tasks based on an image provided from an image sensor; wherein the selected biometric analysis task is performed in a deep neural network that includes a common feature extraction neural network, a plurality of biometric task-specific neural networks and a plurality of expert pooling neural networks that perform the plurality of biometric analysis tasks by: inputting the image to the common feature extraction network to determine latent variables; inputting the latent variables to the plurality of biometric task-specific neural networks to determine a plurality of first outputs; concatenating the plurality of first outputs to form concatenated first outputs; inputting the concatenated first outputs and the latent variables to the plurality of expert pooling neural networks to determine one or more biometric analysis task outputs; and selecting and outputting one or more biometric analysis task outputs.
 14. The method of claim 13, further comprising operating a device based on the selected biometric analysis task output.
 15. The method of claim 13, wherein the plurality of biometric analysis tasks include biometric identification, liveliness determination, drowsiness determination, gaze determination, pose determination, and facial feature segmentation.
 16. The method of claim 13, wherein the common feature extraction neural network includes a plurality of convolutional layers.
 17. The method of claim 13, wherein the plurality of biometric task-specific neural networks include a plurality of fully connected layers.
 18. The method of claim 13, wherein the plurality of expert pooling neural networks include a plurality of fully connected layers.
 19. The method of claim 13, wherein the one or more of first outputs from the plurality of biometric task-specific neural networks are input to a SoftMax function before being concatenated.
 20. The method of claim 13, wherein one or more of the outputs from the plurality of expert pooling neural networks are input to a SoftMax function before being output as biometric analysis task outputs. 